Ethernet technology for wide area networks (WAN) such as metro area networks (MAN) has advanced remarkably accompanying the spread of Wide Area Ethernet (registered trademark) service.
In such networks, link and path redundancy exists and when a failure occurs, by switching to backup links/paths, communication can continue even if a link is lost or trouble at a relay device (hereinafter, “node”) occurs.
For example, when the prescribed spanning tree protocol (STP) or the rapid spanning tree protocol (RSTP), which is an expansion of the STP, is used as an Ethernet (registered trademark) network redundancy scheme, a tree is configured and corrected, enabling failure recovery (see, for example, Japanese Laid-Open Patent Publication No. 2007-258955).
Further, in recent years, Ethernet (registered trademark) network redundancy schemes have been standardized by ITU-T and 1+1 path protection has been prescribed. For example, when a 1+1 path protection scheme is used, an active path and a backup path, which share no links/nodes, are set between a start node and a terminal node. At the start node, packets are transmitted to both paths and at the terminal node, packets that are from the active path are selected. Thus, if failure occurs on the active path, high speed failure recovery is possible by switching to the use of the packets from the backup path.
Nonetheless, when the STP is used, a problem arises in that the configuration and correction of the tree takes time and the switch to the redundant path takes considerable time. Although RSTP resolves the shortcomings of the STP to a certain extent, depending on the location of failure, the switching of paths can take considerable time, like under the STP.
When a 1+1 path protection scheme is used, although high speed failure recovery is possible, operation so that the active path and the backup path do not share links/nodes is costly.